From a materials standpoint, the current state of nanorod arrays includes two general pathways for making the arrays. In the first, free-standing nanorods are grown through a variety of chemical methods and subsequently attached to a substrate in the desired configuration. See Kim et al., J. Am. Chem. Soc., 2001, 123, p. 4360. In the second, nanorods are grown directly on a substrate—either through seeded growth or inside a template using chemical or electrochemical deposition methods.
Regarding the use of templates in the second general above-mentioned pathway, growth of nanorods in nanoporous anodized aluminum oxide templates is now well established. See Masuda et al., Science, 1995, 268, p. 1466; Masuda et al., Appl. Phys. Lett., 1997, 71, p. 2770; Jessensky et al., Appl. Phys. Lett., 1998, 72(10), p. 1173; Yin et al., Appl. Phys. Lett., 2001, 79, p. 1039; and Zheng et al., Chem. Mater., 2001, 13, p. 3859.
Regarding seeded growth of nanorods in the second general above-mentioned pathway; as above, this too is well established (Tian et al., Nature Materials, 2003, 2, p. 821). Such seeded growth can even be used to generate patterned arrays (United States Patent Application Serial No. 20050009224).
Despite advances in creating nanorod arrays, existing methods for making such arrays are still directed to the formation of arrays of nanorods of essentially homogeneous composition. Methods to extend the compositional diversity of such arrays would be extremely useful in that they would provide for multicomponent nanorod arrays useful for a wide range of applications.